A moving-coil earphone is a most ordinary and common earphone. A driving unit of the moving-coil earphone is substantially a small size moving-coil speaker in which a voice coil in a permanent magnetic field drives a vibration membrane (or diaphragm) connected to the voice coil to vibrate. The moving-coil earphone has a high efficiency, can output driving power to an earphone of audio equipment, and is reliable and durable.
A headphone in current market uses a micro-speaker having a diameter of 30 mm, 40 mm, 50 mm, 57 mm, 60 mm and etc. However, for a supra-aural earphone, a speaker having a diameter of 40 mm is too small in size, has a relatively small radiation area, and has an insufficient radiated sound pressure when volume up is pressed. But a speaker having a diameter of 50 mm is relatively big, thus makes the whole set bulky.